1. Field of the Invention
The present invention is related to an ultrasonic imaging apparatus and a method of obtaining ultrasonic images for scanning a 3D region using ultrasonic waves. In particular, the present invention is related to an ultrasonic imaging apparatus and the method of obtaining the ultrasonic images for scanning by varying the transmission/reception conditions of ultrasonic waves, depending on the region.
2. Description of the Related Art
An ultrasonic imaging apparatus scans a predetermined range with repeating transmission/reception of ultrasonic waves and generates ultrasonic images, based on data that has been obtained by the scan.
A 2D array probe comprises a plurality of ultrasonic transducers that are two-dimensionally arranged. The 2D array probe can scan a 3D region using ultrasonic beams. Image processing such as volume rendering (hereinafter, may be referred to as “VR processing”) and MPR (Multi-Planar Reconstruction) processing is applied to volume data that has been obtained by scanning the 3D region, thereby generating 3D image data or image data on an arbitrary cross section.
In this ultrasonic imaging apparatus, the volume rate and image quality of an ultrasonic image have a relationship of trade-off. For example, when obtaining a high-definition ultrasonic image while enhancing the volume rate, it is necessary to scan by narrowing down the 3D scanning region. Lowering the scanning line density of ultrasonic beams by reducing the number of transmission/reception times of ultrasonic beams makes it possible to improve the volume rate. However, the image quality of the ultrasonic image obtained by the scan thereby decreases.
In addition, raising the scanning line density of ultrasonic beams by increasing the number of transmission/reception times of ultrasonic beams enables acquisition of a high-definition ultrasonic image. However, the volume rate during such a scan will decrease.
Thus, as the density of the scanning line of ultrasonic beams is higher, the image quality of the ultrasonic image obtained by the scan improves further, but the volume rate will decrease. Conversely, as the density of the scanning line of ultrasonic beams is lower, the volume rate during the scan improves further, but the image quality of the ultrasonic image obtained by the scan will decrease.
Ultrasonic imaging apparatuses according to the prior art sets a region of interest (ROI) on the ultrasonic image obtained by transmitting/receiving ultrasonic beams and limits the range to be scanned by ultrasonic beams (e.g., Japanese Patent Laid-open Publication 2005-245936).
However, ultrasonic imaging apparatuses according to the prior art usually change the scanning line density of ultrasonic beams for the entire region to be scanned and then scan the entire region in accordance with the changed scanning line density. Therefore, it has been impossible to improve the image quality of only the sites that are necessary for diagnosis among the sites represented in an ultrasonic image obtained by a scan. For example, when obtaining an ultrasonic image of the heart, it has been difficult to improve the image quality of only the heart wall, even while focusing on the heart wall of a heart. Thus, conventionally, it has been possible to adjust the image quality of the entire ultrasonic image only, while it has been difficult to partially adjust the image quality of ultrasonic images.
According to the prior art, when the scanning line density of ultrasonic beams can be changed only in the entire region to be scanned, the following problems arise. For example, when the scanning line density of ultrasonic beams is lowered in the entire region, the volume rate increases, but image quality of the site of interest will decrease. Consequently, a high-definition ultrasonic image suitable for diagnosis cannot be obtained.
In addition, when increasing the scanning line density of ultrasonic beams for the entire region, the entire image quality including the site of interest would increase, but the volume rate will decrease. Therefore, an image that is suitable for diagnosis in which real-time properties need to be ascertained cannot be obtained.
For example, when diagnosing a site in motion such as a heart, real-time properties need to be ascertained. However, when the scanning line density of ultrasonic beams is lowered in the entire region to be scanned in order to improve the volume rate, the image quality of the site of interest such as a heart wall will also decrease. Conversely, when the scanning line density of ultrasonic beams is raised in the entire region to be scanned in order to improve the image quality of the site of interest such as a heart wall, the volume rate will decrease. Consequently, an image suitable for diagnosing a site in motion such as a heart cannot be obtained.